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Concerns about growing carbon dioxide levels in the atmosphere and global warming have made it critical to replace fossil fuels with cleaner, more sustainable alternatives. Hydrogen, a clean energy source, has emerged as a promising possible choice in this area.
Concerns about growing carbon dioxide levels in the atmosphere and global warming have made it critical to replace fossil fuels with cleaner, more sustainable alternatives. Hydrogen, a clean energy source, has emerged as a promising possible choice in this area.
Splitting water using electricity in the presence of a catalyst, also known as “electrocatalytic water splitting,” is the cleanest of the various ways available for hydrogen creation. Unfortunately, to maintain a respectable efficiency, the process necessitates the use of expensive and rare noble metal catalysts, such as platinum. As a result, large-scale industrial uses have been limited.
Transition metal-based catalysts, such as oxides, sulfides, and hydroxides of cobalt, nickel, and iron, are a reasonably affordable choice. There is, however, a catch: electrocatalytic water splitting is made up of two half-reactions: the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) (OER). At the anode in OER, water molecules are oxidized to produce oxygen and positive hydrogen ions (positively charged electrode). The hydrogen ions then go through the electrolyte to the cathode (the negatively charged electrode), where they are reduced and hydrogen is produced (HER). Most transition metal-based catalysts that have been reported so far can only catalyze HER or OER. This results in a more difficult setup and a higher total cost.
In light of this, researchers from Chung-Ang University in Korea have created a novel heterostructured catalyst made up of hollow cobalt sulfide (CoSx) and nickel-iron (NiFe) layered double hydroxide (LDH) nanosheets that accelerate both half-reactions concurrently in a recent study. On March 15, 2022, this work was made accessible online, and on April 16, 2022, it was published in Volume 18 Issue 16 of the journal Small.
“Intricately integrating OER-active NiFe LDH and HER-active catalysts into a heterostructure is a feasible technique for constructing extremely effective catalysts for water splitting,” explains Assistant Professor Seung-Keun Park, who led the work. “Hollow HER catalysts are thought to be appropriate for this purpose because of their high surface area and open structure.” Metal-organic frameworks (MOFs) have been discovered to be effective precursors for constructing hollow structures. A MOF-based hollow catalyst with NiFe LDH, on the other hand, has yet to be described.”
As a result, the researchers electrochemically deposited NiFe LDH nanosheets on the surface of hollow CoSx nanoarrays supported on nickel foam in a controlled way. “By combining an active HER catalyst, CoSx, with an OER catalyst, NiFe LDH, we may achieve the better bifunctional catalytic activity,” Dr. Park explains.
Indeed, the catalyst was able to generate a high current density of 1000 mA cm-2 in both half-reactions at low cell voltages, indicating that it might be used in large-scale water splitting. This was due to the existence of several active sites on the catalyst heterostructure, which allowed electrolyte penetration and gas release during the reactions, according to the researchers. An electrolyzer based on this catalyst also achieved a high current density of 300 mA cm-2 at a low cell voltage and total water splitting durability of 100 hours.
“Our catalyst’s improved electrocatalytic capabilities are likely attributable to its unique hierarchical heterostructure and component synergy.” “We feel that our effort will get us closer to creating a zero-emission society,” adds Dr. Park, who is upbeat.
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